P43B-2121
Chemical Composition of Diagenetic Features at Lower Aeolis Mons, Mars as Measured by Curiosity’s APXS
Thursday, 17 December 2015
Poster Hall (Moscone South)
Jeff A. Berger1, Mariek E Schmidt2, Ralf Gellert3, Nick Boyd3, John L Campbell3, Elstan Desouza3, Martin R Fisk4, Glynis M Perrett3, Lucy M Thompson5, Scott VanBommel6 and Albert S Yen7, (1)University of Western Ontario, London, ON, Canada, (2)Brock University, St Catharines, ON, Canada, (3)University of Guelph, Guelph, ON, Canada, (4)Oregon State Univ, Corvallis, OR, United States, (5)University of New Brunswick, Planetary and Space Science Centre, Fredericton, NB, Canada, (6)University of Guelph, Norwich, ON, Canada, (7)NASA Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
Curiosity’s APXS investigation of the Murray Fm. (sols 755 - 950) at lower Aeolis Mons (Mt. Sharp) in Gale Crater, Mars has revealed (Mg, Ni)-sulfate diagenetic features and dark gray Ca-rich veins. The (Mg, Ni)-sulfate features occur as ~2 cm wide dendritic and botryoidal concretions that stand out in relief ~1 cm above the mudstone surface. APXS rasters over the features (Moenkopi, Mammoth, Morrison, Rosamond, Potatoe; sols 758 - 810) resulted in 1:1 molar variation of S and Mg consistent with a MgSO4 phase. The sulfate is not pure; the features are a mixture of 10 - 15% MgSO4 with the host mudstone. This mixture suggests the sulfates precipitated within pre-existing pore spaces, or were partially dissolved and replaced by sediment, preserving the crystal morphology. The sulfate features are enriched in Ni (2000 – 4250 ppm), indicating Ni-sulfate. The Murray Fm. mudstones that host the diagenetic features range to high SiO2 (60–73 wt%) and have bulk elemental signatures that are consistent with alteration by acid leaching. Low MgO (3.0 wt%) and low Ni (100 – 300 ppm) in the most apparently altered (highest SiO2) mudstones may link the acidic alteration with the fluids that formed the (Mg, Ni)-sulfates. Diagenetic Ca-sulfate-bearing veins that were abundant across Aeolis Palus persist at lower Aeolis Mons. A new vein type containing dark gray material as a separate crystalline phase within white Ca-sulfate veins was discovered in a cluster of veins in the Murray Fm. (Coalville, Alvord Mt., Amboy; sols 930 – 948). APXS rasters of the dark-toned material indicate high CaO (20 - 30 wt%) without concomitant increases in SO3. Ge (up to 650 ppm; 6.5X surrounding bedrock) and MnO (up to 1.0 wt%; 4X surrounding bedrock) are both enriched in the dark veins. These chemical observations are consistent with fluorite, although F (L.O.D. >5%) is not detectable in APXS spectra. The diagenetic features indicate that Ca, Mg, and Ni were mobilized with S in aqueous fluids, and that F may have played a role in the acidic alteration of the Murray Fm.
